The present invention relates to ion and electron optical systems, such as mass spectrometer (“MS”) systems. Mass spectrometer systems may, for example, be used to analyze the chemical composition of subject samples. Generally, such systems ionize the atoms and molecules present in a subject sample. Once ionized, the ions are transferred into a mass analysis region where they are separated, or filtered, according to their mass-to-charge ratio (m/z) to create a mass spectrum. A charged-particle detector of the mass spectrometer system then analyzes the ions in order to identify their mass and velocity distribution. From this, information useful in characterizing the chemical composition of the sample can be determined.
Ion and electron optical systems, such as mass spectrometer systems, generally require a reduced pressure environment and therefore include a vacuum system for lowering the pressure throughout. To ionize the sample, mass spectrometer systems also include an ionization source such as an electron ionizer (“EI”) or chemical ionizer (“CI”). One type of mass spectrometer system, a gas chromatograph (“GC”) mass spectrometer system, further includes a gas chromatograph to separate volatile and non-volatile compounds prior to providing them for ionization.
The systems generally also include a mass separator or mass analyzer. In some systems, the mass separator includes an electromagnet for deflecting ions in the beam. Depending on the mass and charge of the ions, the magnitude of deflection varies. Generally ions having a higher mass, deflect less. Species of ions present in the sample may therefore be separately studied by varying the magnetic field.
In some other systems, the mass separator includes a quadrupole mass filter consisting of four parallel rods. For example, two opposite rods may have a positive applied potential while the other two rods have a negative potential. The applied voltages affect the trajectory of ions traveling down the flight path centered between the four rods. For given voltages, only ions of a certain mass-to-charge ratio pass through the quadrupole filter and all other ions are thrown out of their original path. A mass spectrum may therefore be generated by varying the voltages.
The various components of ion and electron optical systems are subject to high temperatures, stress, and contact with any number of chemical compounds. Traditionally, ceramics have been used for various components due to their desirable chemical and electrical properties. However, the ceramics which are presently used often do not provide the necessary structural strength and are, therefore, prone to fracture damage or breakage. Often, the thermal expansion of adjacent metal components causes the ceramic components to break. This can cause misalignment, ceramic dust contamination and electrical insulation breakdown in the mass spectrometer. Other materials which are used in ion and electron optical systems have better strength capabilities, but are unstable and lose electrical insulation properties at high temperatures.